subgroup vs grouping

subgroup and grouping both are nouns.

Word	Noun	Adjective	Verb	Adverb
subgroup	Yes	No	No	No
grouping	Yes	No	No	No

As nouns, grouping is a hypernym of subgroup; that is, grouping is a word with a broader meaning than subgroup:

Other hypernyms of subgroup include group.

subgroup (noun)	grouping (noun)
(mathematics) a subset (that is not empty) of a mathematical group	any number of entities (members) considered as a unit
a distinct and often subordinate group within a group	the activity of putting things together in groups
	a system for classifying things into groups